Advanced CFD modelling of air and recycled flue gas staging in a waste wood-fired grate boiler for higher combustion efficiency and greater environmental benefits

Boštjan Rajh, Chungen Yin, Niko Samec, Matjaz Hribersek, Filip Kokalj, Matej Zadravec

Research output: Contribution to journalJournal articleResearchpeer-review

17 Citations (Scopus)

Abstract

Grate-fired boilers are commonly used to burn biomass/wastes for heat and power production. In spite of the recent breakthrough in integration of advanced secondary air systems in grate boilers, grate-firing technology needs to be advanced for higher efficiency and lower emissions. In this paper, innovative staging of combustion air and recycled flue gas in a 13 MWth waste wood-fired grate boiler is comprehensively studied based on a numerical model that has been previously validated. In particular, the effects of the jet momentum, position and orientation of the combustion air and recycled flue gas streams on in-furnace mixing, combustion and pollutant emissions from the boiler are examined. It is found that the optimized air and recycled flue gas jets remarkably enhance mixing and heat transfer, result in a more uniform temperature and velocity distribution, extend the residence time of the combustibles in the hot zone and improve burnout in the boiler. Optimizing the air and recycled flue gas jet configuration can reduce carbon monoxide emission from the boiler by up to 86%, from the current 41.0 ppm to 5.7 ppm. The findings of this study can serve as useful guidelines for novel design and optimization of the combustion air supply and flue gas recycling for grate boilers of this type.
Original languageEnglish
JournalJournal of Environmental Management
Volume218
Pages (from-to)200-208
Number of pages9
ISSN0301-4797
DOIs
Publication statusPublished - Jul 2018

Keywords

  • Waste wood-fired grate boiler
  • Computational fluid dynamics (CFD)
  • Air/flue gas staging
  • Boiler performance
  • Flow uniformity
  • Mixing process
  • Pollutant emissions

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